Method of degassing cathodes of electron discharge tubes



Patented Jan. 31, 1933 ,eaiaz WILHELM ALBRECHT, OF VOORBURG,

CORPORATION OF AMERICA, A CORPORATION OF DELAWARE NETHERLANDS, ASSIGNOR 'ro RADIO METHOD OF DEGASSING CATI-IODES F ELECTRON DISCHARGE TUBES No Drawing. Application filed February 9, 1932, Serial No. 591,923, and in France March 24, 1931.

This invention relates to an improved method of depriving an electrode, such as the cathode, of an electron discharge tube of occluded gases.

For depriving of occluded gases the anode and other electrodes which cooperate with the cathode of an electron discharge tube it has been proposed to subject them to a high frequency heating. It is also known to free the cathode from occluded gases by raising it to a temperature higher than the normal temperature of operation. If the tube comprises an indirectly heated cathode, the heating may be effected by means of an intense current passed through the heater. It has been found that to sufficiently degas the cathode, or deprive it of occluded gases the heater must often be raised to such a high temperature that it is damaged.

The invention has for its object to remove this inconvenience. According to the invention an electrode, such as a cathode, of an electron discharge tube is deprived of cocluded gases by bombardment by electrons emitted by a material applied upon one of the other cooperating electrodes of the tube. For

this purpose, some active electron emitting material may be secured, for example, to the inside of the anode, whereby a very efficient degassing of the cathode can be ensured by electrons from said material without causing any damage to the cathode. Consequently, the invention can be used with advantage for depriving an indirectly heated cathode of occluded gases.

In order that the invention may be clearly understood and readily carried into effect, one embodiment thereof will now be described more fully.

In this embodiment the invention is applied to an electron discharge tube for receiving or amplifying electric oscillations and compris ing an anode and one or more grids which are normally cool during operation of the tube, and surround an indirectly heated cathode.

This cathode may consist, for example, of a small nickel tube which is coated on the outside with electron emitting material such as barium and strontium oxides, and having inside it a heater which may be separated from the nickel tube by insulating material such as magnesla.

"The anode prior to being mounted in the tube has secured to its inside wall a little barium azide. During the exhaustion of the tube the anode is heated by means of a high frequency coil or field so that the nitrogen escapes from the azide and barium remains. When the vacuum in the tube becomes good enough, preferably so high that no deleterious ionization will be produced, the cathode is given a high positive potential relative to the anode and the anode is heated, preferably by the high frequency coil, so that the barium on it emits electrons. Under the inr fiuence of the electric field due to the difference inpotential between the cathode and anode these electrons from the material on the anode move at high speed towards the cathode on which they impinge. Owing to ,1 the bombardment by the electrons the cathode is raised to such a high temperature that the occluded gases are expelled from the cathode, and may be removed from the tube by the ump. 1

After the degassing of the cathode the anode'may be raised by the'high frequency coil to a higher temperature so that the barium volatilizes and deposits on the cathode where, after oxidation, if necessary, it constitutes an electron emitting layer.

The active substance, such as barium, tha yields the electrons for the bombardment of the'cathode maybe applied to an electrode other than the anode, for example, to a grid, and the connections may be so made that a grid is bombarded by electrons from an ac tive material on the anode or on another grid.

I claim:

1. The method of degassing the cathode of an electron discharge device having a cathode and a cooperating electrode which consists in applying an electron emitting material to said cooperating electrode, heating said cooperating electrode to cause said material to ps emit electrons, and maintaining said cathode sufficiently positive with reference to said cooperating electrode to cause bombardment of said cathode by electrons from said material.

2. The method of degassing the cathode of an electron discharge device comprising an envelope enclosing a cathode and a cooperating normally cool electrode surrounding said cathode, which consists in applying to the inside of said electrode an electron emitting material, evacuating said envelope, heating said electrode to cause said material to emit electrons, and producing between said cathode and said electrode, an electric field which causes electrons from said materialto bombard said cathode.

3. The method of degassing an electrode of an electron discharge device comprising a plurality of electrodes some of whlch are normally cool during operation of the device, which comprises placing an electron emitting materialon oneof said normally cool electrodes, heating said normally cool electrode to cause said material to emit electrons, and maintaining one of the other of said electrodes sufficiently positive to cause it to be bombarded by electrons from said material. 1 v V 4. The methodof treating an electron discharge tube having a cathode and an anode which comprises placing an electron emitting material on said anode adjacent said cathode,

heating said anode to cause said material to emit electrons, maintaining said cathode suf ficiently positive with'reference to said anode to cause bombardment of said cathode by the electron from said material, and heating said anode to a higher temperature to drive off said electron emitting material.

5; The method of treating an'electron discharge tube having a cathode and an anode surrounding it which comprises placing barium azide on the inner wall of said anode, heating said anode to decompose said barium azide and leave barium on said anode, further heating said anode to cause said barium on it to emit electrons, maintaining said cathode sufiiciently positive with reference to said anode to cause the electrons from said barium to bombard said cathode, and'still further heatingisaid anode to drive off said barium.

, VVILHELM ALBRICHT. 

